The study observed high concentrations of metals such as mercury, arsenic and cadmium in animals including ducks, muskrats, moose and beavers. Bitumen upgrading and extraction is a "major emitter" of these chemicals, the news release said.

The report was peer-reviewed by Health Canada and other agencies.

While no one from the board seems to have explained to O'Connor why he was dismissed, Mikisew Cree Chief Steve Courtoreille told The Edmonton Journal that O'Connor hadn't been in Fort Chipewyan for years.

O'Connor left the community in 2007 and has since provided on-call advice, the Journal said.

"He hasn't been in Fort Chip for a number of years, so how can he be a strong advocate when he is not in the community to come and talk with us and talk to the people?" Courtoreille asked.

O'Connor, meanwhile, said no one expressed any issues to him about working from outside the community.

Nevertheless, he told APTN that he will continue speaking up for Fort Chipewyan and pushing the provincial government to carry out a study of cancer rates in the area.

"It's like a part of you is gone," O'Connor said of his firing. "Maybe in a few months it will be a little bit less, but I know I won't stop contact with the community that's for sure."